This invention relates to a machine such as an earth moving machine, that is a machine having a body movable by its own propulsion means over the ground, and a boom mounted on the body, the boom and/or an additional arm mounted thereon, known commonly as a "dipper" arm, carrying an implement such as a bucket or other excavating implement, forks or any other implement for handling loads, the body and/or the boom and/or dipper arm and/or implement being relatively movable to enable operations to be carried out, such as earth moving, by the implement.
In recent years, there has been a need for an earth moving machine having long reach, that is the implement has to be able to carry out operations at a considerable distance from the body of the machine. Whereas the use of hydraulic rams in earth moving machines is well known for achieving relative movement between the body and/or the boom and/or the dipper arm and/or the implement, hydraulic rams are not operationally satisfactory where very large leverages are encountered, e.g. when the boom and/or dipper arm are long and the implement is a considerable distance from the body.
Hence, it has been proposed to use a cable and winch arrangement, to move the implement towards the body during an operation. Such an arrangement is shown in European specification EP 0077684. The machine disclosed in this specification is also provided with a counterweight which is slidable along the boom to vary the counterbalance of the machine as the implement is moved towards and away from the body.
The machine has a counterweight and a dipper arm ram both mounted on the boom, the dipper ram moving the counterweight along the boom to cause the dipper arm to pivot outwardly by means of a cable which is attached at one end to the counterweight and at the other end to the dipper arm.
The cable is thus economically used both for moving the counterweight to balance the machine and to enable the dipper arm to be pivoted out, with minimum stress and strain on the remainder of the boom structure.
However, such a machine also has disadvantages.
First, in this prior machine, a further cable is used with a winch means for moving the implement towards the body in addition to the cable which allows for automatic adjustment of the position of the counterweight in response to movement of the implement. So many cables are undesirable.
Secondly, the counterweight, by being mounted on the boom, is very high above the ground and this can lead to lateral instability of the machine during operation.
Thirdly, the boom is mounted intermediate its ends on the body so as to provide a tail part which extends rearwardly of the mounting, on which the counterweight slides. Because part of the boom extends behind the mounting, the angle through which the boom can pivot relative to the body about a generally horizontal axis, is restricted and hence the working range of the implement is restricted.
Fourthly, the boom in the arrangement of European specification EP 0077684 must necessarily be straight because of the cable which runs along the top of the boom and is connected to the dipper arm and counterweight.
It is desirable to be able to provide a cranked or curved boom where less loading height is needed but greater depth access is required. If a curved boom were used in the arrangement of European specification EP 0077684, pulleys and the like would be required to guide the cable, and this would result in premature wear of the cable and this would be unsatisfactory in practice.
The body of the machine is only satisfactorily suited to receiving booms and dipper arm arrangements adapted for long reach operation and if it is required to exchange the long reach boom and dipper arm arrangement for a conventional shorter reach arrangement, for example having a hydraulic ram which is effective to move the dipper arm both towards and away from the body, the part of the boom which extends rearwardly of the mounting has to be retained, where a counterweight is required, thus severely restricting the working range of the implement.
Accordingly, it is an object of the present invention to provide a new or improved machine which overcomes these disadvantages and provides additional advantages.